And how do you get back to the home screen while using an app? Screaming, "There's no place like home! There's no place like home!" and clicking your heels together, hoping Siri will get it? I do hope they get rid of every single bug they have now that freezes the touch screen, too. I'd hate for the only way to reboot your machine to be to take it for service.
I am guessing some use of 3D touch, a gesture, or a combination of both.